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Avoid blurry photos by learning to choose the correct focus mode on reflex cameras

You have to be very clear about the concepts of the different autofocus modes. In practice the focus areas are not always what they promise or require a learning period.
Surely it has happened to you that you had before you the perfect moment for a photo and, however, when you review the result you realize that the image is not as sharp as you expected. The causes can be various, starting with a jitter caused by an incorrect shutter speed, but it is also very common that the cause is a bad focus because we have made a bad choice of the AF mode of our camera.
This problem is common in the novice but also in those who release a new camera, perhaps one of the last batch that incorporates hybrid AF systems with a multitude of focus areas and very sophisticated logarithms that promise precision and speed never seen in photography. . However, in practice they are not always what they promise or require a learning period, in addition to making it necessary to have very clear concepts about the different modes of automatic focus.

As you may know, there are basically two modes, the AF-S (single or single autofocus, also known as One Shoot) and AF-C (continuous autofocus, also known as AI Servo), plus a third, AF-A (autofocus). automatic) that appears in the most modern cameras. We have talked about these several times (including of course in our Photography Course), but now we are going to review them from a practical point of view. That is, paying special attention to when we should use one or the other mode depending on the scene in question that we want to capture.

Choosing the focus area

But first we have to talk about another characteristic that is crucial to know how to use AF well, and which is none other than the choice of the focus area to use and, consequently, the number of focus points that will come into play.

What we should know is that, apart from the different AF modes, you can also choose between different ways of selecting the area or focus point. In this we are not going to go into depth, since they depend a lot on the type of camera, but it is convenient to know that we can choose (basically) between the camera deciding which is the preferred point or area of ​​focus at each moment or that we do it U.S.

Obviously this second option is the one we recommend the most but we also have to know that we can choose several options. One would be the most classic and involves deciding to focus the camera only on the center point / area, and reframe if necessary. The other, more modern (and available depending on the model), is the one that makes it possible to choose on the fly the place (point or area) where we want the camera to focus.

The first option, that of letting the camera do the work by itself, we recommend less because it is evident that the cameras do not always behave as expected, especially in situations with many elements or when they move quickly. In these cases it is where the most advanced cameras, the professional type, which usually incorporate very sophisticated focusing systems and algorithms, shine.



Many SLRs include a focus select button similar to the one in the image

For the rest, although the models are becoming more advanced and are even able to follow faces automatically, it is better to resort to manual selection of the place we want to focus on. Although everything is a matter of knowing and thoroughly testing your camera to know how reliable its AF system is.

If the subjects do not move

We have already moved on to the focus modes themselves and, as we mentioned, we do so taking into account the situation. The first would be the one that perfectly describes the title, when the element we want to capture has no movement, for example a still life or a static landscape.

In this case the choice is clear and the ideal mode is the simple autofocus, AF-S, which focuses taking into account the distance at which the subject is in the chosen area point. Thus, the element will remain sharp (as long as it does not move) since the camera will lock the focus at that point as long as we keep the shutter-release button pressed halfway (or the AF-On button).

Thanks to this system we can easily make a change in the composition of the photograph once we have focused. For example because we have done it with the central point but we do not want the focused subject to be centered. In these cases, by the way, leaving the choice of the focus point to the camera is not recommended, in fact it would be even more convenient to focus manually.



If there are moving elements

The opposite case, that of the subjects in which there are moving subjects, are those in which we have to opt for continuous automatic focus, AF-C, which will be in charge of keeping the element in question focused even though it moves ( and as long as we keep the appropriate button pressed). The best example is action and sports photography, where the use of this focus mode is more than widespread and very necessary.




For moving subjects, the AF-C is undoubtedly the best option. Jamie Street Photo
In these cases, it might be advisable to let the camera choose the point or area of ​​focus, but always sticking to what we said before: To the solvency of our camera for moving focus. Because it will be useless if we are continuously focusing if what we have selected is not what we want to have in focus. Therefore, lately we are seeing modern systems that allow you to choose the AF point / area very quickly through the touch screen or through a small joystick.

If the subject does not move but can do so ...

It would be a third option associated with the automatic autofocus mode, AF-A, which, as you may have already guessed, is a hybrid between single and continuous AF. This system focuses in principle as the static mode, focusing on an immobile element, but the focus may vary if this subject begins to move, as would be the case, for example, with photographic portraits.



In portrait photography the AF-A mode can help prevent possible out of focus if the subject is moved unintentionally. Prasanna Kumar photo

That is, it is a mode that combines the best of the other two, so in principle it is highly recommended to choose it by default. Although again the most important thing is to know the capabilities of our camera and know how it behaves, to decide one way or another when shooting.

Other things to consider

We're done with those other little things you need to know, especially if you're a novice, to make sure you're not going to have a blurry photo because of the focus system. The first for example is that you take into account the minimum focus distance of the lens you are using, lest your camera does not focus because you are too close (it happens more often than it may seem).

Another reason that may cause the focus to not be correct is that you are trying to focus on a complicated subject that has little contrast, or in a very low light situation that prevents the AF system from working properly (again, everything depends on your camera in particular). And a third problem that can negatively affect the focus of an image is that we are working with an extremely shallow depth of field that makes it very difficult to hit the exact spot.
Avoid blurry photos by learning to choose the correct focus mode on reflex cameras Revisado por elcidop en 15:57 Clasificación: 5

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